Rainbow-electronics MAX1400 User Manual download pdf (Page 31)

MAX1400

+5V, 18-Bit, Low-Power, Multichannel,

Oversampling (Sigma-Delta) ADC

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Strain Gauge Operation

Connect the differential inputs of the MAX1400 to the

bridge network of the strain gauge. In Figure 16, the

analog positive supply voltage powers the bridge net-

work and the MAX1400 along with its reference voltage.

The on-chip PGA allows the MAX1400 to handle an

analog input voltage range as low as 20mV full scale.

The differential inputs of the part allow this analog input

range to have an absolute value anywhere between

AGND and V+.

Temperature Measurement

Figure 17 shows a connection from a thermocouple to

the MAX1400. In this application, the MAX1400 is oper-

ated in its buffered mode to allow large decoupling

capacitors on the front end. These decoupling capaci-

tors eliminate any noise pickup form the thermocouple

leads. When the MAX1400 is operated in buffered

mode, it has a reduced common-mode range. In order

to place the differential voltage from the thermocouple

on a suitable common-mode voltage, the AIN2 input of

the MAX1400 is biased at the reference voltage, +2.5V.

DIVIDER

CLOCK

GEN

MODULATOR

DIGITAL

FILTER

V+

V+ V

AGND

REFIN+

MUXOUT+ ADCIN+

REFIN-

MUXOUT- ADCIN- AGND DGND

AIN1

AIN2

SWITCHING

NETWORK

ACTIVE

GAUGE

DUMMY

GAUGE

REF

ANALOG SUPPLY

ADDITIONAL

ANALOG

AND

CALIBRATION

CHANNELS

INTERFACE

AND

CONTROL

SCLK

DIN

DOUT

INT

RESET

CLKIN

CLKOUT

PGA

DAC

MAX1400

BUFFER

Figure 16. Strain-Gauge Application with MAX1400

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Rainbow-electronics MAX1400 User Manual Page 31

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